Polyamide molding compositions

ABSTRACT

A thermoplastic molding composition comprising polyamide is disclosed. The composition that contains vinyl (co)polymer and an optional solvent is useful in application where inhibited crystallization of polyamide is desirable, including laser-welding.

FILED OF THE INVENTION

[0001] The present invention relates to thermoplastic moldingcompositions and more particularly to polyamide molding compositions.

SUMMARY OF THE INVENTION

[0002] A thermoplastic molding composition comprising polyamide isdisclosed. The composition that contains vinyl (co)polymer and anoptional solvent is useful in the application where inhibitedcrystallization of polyamide is desirable, including laser-welding.

BACKGROUND OF THE INVENTION

[0003] Polyamides are distinguished by a large number of advantageousproperties, such as e.g. high toughness, high temperature resistanceetc., which guarantee them a secure market position in the engineeringthermoplastics sector. These basic properties of the polymer aregenerally modified by the addition of fillers or additives. Polymer andadditives together form the so-called molding composition. Polyamidemolding compositions are used in many applications. Injection moldedparts, e.g. for the automotive market, or extrudates such as films orhollow articles for the packaging sector may be mentioned as examples.

[0004] Films and hollow articles containing a polyamide layer aredistinguished by a large number of advantageous properties. Particularlyworthy of mention are good optical properties, such as high transparencyof films or hollow articles with high surface gloss. Also significantare the good mechanical properties, such as high toughness, highpuncture resistance, high tear propagation resistance and others. Easeof production and ease of further processing are added to these.

[0005] Of particular significance for many areas of application forfilms and molding compositions, particularly for use in the packagingsector, e.g. for foodstuffs or cosmetics, is control of the rate ofcrystallization of the material used, to provide a specific influence onproperties such as e.g. shrinkage or impact strength.

[0006] In the area of the use of polyamide in the production of films, afundamental distinction must be drawn between the flat film productionprocess and the blown film production process.

[0007] Particularly in the area of application in the blown film sector,polyamides with slower crystallization than conventional polyamide 6 arenecessary to enable the primary tube to be blown and stretched in theblown film production process before the film has reached too high adegree of crystallization.

[0008] At present, this goal is achieved by the use of copolyamides. Themost widespread copolyamide in blown film extrusion is a copolyamideconsisting of polyamide 6 and polyamide 66, which usually containsbetween 15 wt. % and 20 wt. % polyamide 66.

[0009] However, other copolyamides with delayed crystallization are alsodescribed (e.g. EP-A 561 226). Here, copolyamides of caprolactam,isophthalic acid and hexamethylene diamine with reduced crystallinitycompared with conventional polyamides are described. Increasedtransparency of the multi-layer film claimed is achieved by the reducedcrystallinity after processing.

[0010] These copolyamides are conventionally produced not by thecontinuous tubular reactor process, which is widespread for polyamide 6,but by special processes, as described in EP-A 98 412, EP-A 393 546 orWO-A 9421711.

[0011] It is known that the transparency of polyamides may be improvedby incorporating poly-N-vinylpyrrolidones at the polymerization orcompounding stage (DE-A 1 595 613).

[0012] The Japanese patent application JP-A 2002306059 describes thecoextrusion of a blend of 96% polyamide 6-polyamide 66 copolymer with 4%of a crosslinked N-vinylpyrrolidone to produce packaging for foodstuffshaving moderate water vapor permeability and a good oxygen barrier.

[0013] The use of poly-N-vinyllactam or poly-N-vinylpyrrolidones is alsowidespread in the fiber production sector. Here, for example, toincrease the hydrophilic properties, 3 wt. % to 15 wt. % of the abovecompounds are incorporated by compounding. A high proportion ofpoly-N-vinyllactam or poly-N-vinylpyrrolidone has a negative effect onthe yellowness index, however (EP 802 268).

[0014] In the area of compounded products, nigrosine base isconventionally used to slow down crystallization, but this leads to ablack discoloration of the product.

[0015] For applications such as the laser transmission welding ofpolyamide moldings, materials with the lowest possible crystallinity areneeded, since the transmission of laser light decreases with increasingcrystallinity. Basic principles of laser transmission welding aredescribed in the specialist literature (Kunststoffe 87 (1997) 3,348-350; Kunststoffe 88 (1998) 2, 210-212; Kunststoffe 87 (1997) 11,1632-1640; Plastverarbeiter 50 (1999) 4, 18-19; Plastverarbeiter 46(1995) 9, 42-46).

[0016] A prerequisite for the use of laser beam welding is that theradiation emitted by the laser first passes through a joining partner,which is sufficiently transparent for laser light of the wavelengthused, and is then absorbed by the second joining partner in a thin layerof a few 100 μm and converted to heat, which leads to melting in thecontact zone and finally to the bonding of the two joining partners by aweld. While it is true that, in the wavelength range of the lasersconventionally used for thermoplastic welding (Nd:YAG laser: 1060 nm;high-performance diode laser: 800-1000 nm), partially crystallinethermoplastics such as polyamides, e.g. polyamide 6 (PA6) and polyamide66 (PA66) are transparent or laser-translucent, the transmission isoften inadequate for good weldability, and so modifications are requiredfor higher transmission.

[0017] The nigrosine base does indeed reduce crystallinity, but in thefrequency range of 800-1100 nm which is of interest for lasertransmission welding, it has marked self-absorptions.

[0018] The object of the present invention consequently is to develop apolyamide, preferably polyamide 6, composition in which crystallizationis inhibited that is characterized by the absence of any undesirablediscoloration.

DETAILED DESCRIPTION OF THE INVENTION

[0019] Surprisingly, it has now been found that, by adding vinylhomopolymers and/or copolymers of vinyl monomers and preferably asolvent to the polyamide, it has been possible to achieve this object.

[0020] Crystallisation inhibition can be achieved preferably withpoly-N-vinyllactam and poly-N-vinylpyrrolidone, as well as copolymersconsisting of vinyllactam, and/or vinylpyrrolidone and other vinylmonomers, such as e.g. vinyl acetate and/or vinylimidazole and/orquaternized vinylimidazole and/or vinyl acrylate and/or methacrylates,such as e.g. methyl methacrylate, sodium methacrylate or cyclohexylmethacrylate and/or acrylamide and/or acrylonitrile and/orN-vinylcarbazole and/or styrenes, such as e.g. p-aminostyrene, with gooddistribution in the polymer matrix. For this homogenisation, a solventfor the homopolymers or copolymers can be advantageous according to theinvention.

[0021] The invention therefore provides compositions containing

[0022] A) polyamide and B) vinyl homopolymers and/or copolymers of vinylmonomers and preferably a solvent.

[0023] Preferred B) vinyl homopolymers and/or copolymers of vinylmonomers are poly-N-vinyllactam and poly-N-vinylpyrrolidone, as well ascopolymers consisting of vinyllactam, and/or vinylpyrrolidone and othervinyl monomers, such as e.g. vinyl acetate and/or vinylimidazole and/orquaternised vinylimidazole and/or vinyl acrylate and/or methacrylates,such as e.g. methyl methacrylate, sodium methacrylate or cyclohexylmethacrylate and/or acrylamide and/or acrylonitrile and/orN-vinylcarbazole and/or styrenes, such as e.g. p-aminostyrene.

[0024] Preferred amount of B is 0.005-5 wt. %, particularly preferably0.005-1 wt. % and especially preferably 50-8000 ppm based on the weightof the composition.

[0025] As the solvent C, water, alcohols, such as e.g. polyethyleneglycols, ketones, glacial acetic acid, chlorinated hydrocarbons andphenols are preferred.

[0026] Particularly preferred are polyethylene glycols with a molecularweight of between 100 g/mol and 2,000 g/mol, and especially preferredare polyethylene glycols with an average molecular weight of between 200g/mol and 600 g/mol.

[0027] Solvent C: preferred amounts are 0.001-5 wt. %, particularlypreferably 0.001-1 wt. % and especially preferably 300-4000 ppm, basedon the weight of the composition.

[0028] In the case of concentrations of B of less than 5,000 ppm, a C)solvent for poly-N-vinyllactam or poly-N-vinylpyrrolidone is preferredin which the poly-N-vinyllactam or poly-N-vinylpyrrolidone is applieddirectly on to the granules in solution.

[0029] In addition, in the case of molding compositions for processingby injection molding or extrusion (profiles, blow-moldings), the moldingcompositions may contain conventional additives and colorants.

[0030] The invention also provides the use of the inventive compositionsfor the production of polyamide molding compositions and their use forthe production of films, hollow articles, injection moldings andextruded profiles.

[0031] The invention also provides preferably single-layer ormulti-layer films or hollow articles containing at least one layer ofthe inventive molding composition.

[0032] The invention additionally provides packaging containing a filmor a hollow article comprising the inventive composition.

[0033] The invention additionally provides moldings bonded together bylaser transmission welding in which at least the part facing the lasersource comprises the inventive composition.

[0034] Preferred, particularly preferred or especially preferred areembodiments that make use of the parameters, compounds, definitions andexplanations mentioned as preferred, particularly preferred orespecially preferred.

[0035] However, the definitions, parameters, compounds and explanationslisted above, either general or listed in preferred areas, may also becombined with one another, i.e. between the respective areas andpreferred areas.

[0036] The polyamide contained in the polyamide layer of the moldingcompositions, films or hollow articles according to the invention is aknown, aliphatic or aromatic or partially aromatic homopolyamide orcopolyamide or a mixture of several polyamides. For example, andindependently of one another, PA6, PA66, PA 11, PA12, PA 46, PA610,polyamide 6, polyamide 10, polyamide 12, polyamide 66, polyamide 610,polyamide 6I, polyamide 612, polyamide 6/66, polyamide 6I/6T, polyamideMXD6, polyamide 6/6I, polyamide 6/6T, polyamide 6/IPDI and copolymers,as well as polymer mixtures of these groups, are preferably used.

[0037] PA 6 or PA 66 or a copolyamide of caprolactam units and unitsderived from hexamethylenediamine and isophthalic acid orhexamethylenediamine and terephthalic acid or hexamethylenediamine andadipic acid is particularly preferably used. These units derived fromhexamethylenediamine and isophthalic acid or hexamethylenediamine andterephthalic acid or hexamethylenediamine and adipic acid are calledcopolyamide proportions. Copolyamide proportions of 0-50 wt. % arepreferred, copolyamide proportions of between 0 and 25 wt. % areparticularly preferred and 0-15 wt. %, based on A, are especiallypreferred.

[0038] The modification of the polyamides according to the inventionpreferably takes place with poly-N-vinyllactam andpoly-N-vinylpyrrolidones having weight average molecular weights of20,000 g/mol to 2,000,000 g/mol; polyvinylpyrrolidones having molecularweights of between 50,000 g/mol and 1,500,000 g/mol are particularlypreferred and polyvinylpyrrolidones having molecular weights of approx.1,300,000 g/mol are especially preferred.

[0039] The films or hollow articles according to the invention mayinclude one polyamide layer or have a multi-layer construction. In thecase of the multi-layer construction, the other layers may include e.g.polyolefins, such as e.g. polyethylene or polyethylene copolymers, suchas e.g. copolymers of ethylene and acrylic acid or methacrylic acid orbarrier polymers, such as e.g. polyvinylidene chloride or copolymers ofethylene and vinyl alcohol or of other polyamide layers.

[0040] The molding compositions, films, hollow articles, profiles orinjection moldings according to the invention are produced by knownmeans, e.g by extrusion, coextrusion, coating, laminating, blow moldingor injection molding processes. In the case of films, the extrusion orcoextrusion may take place e.g. by the so-called chill roll process orby the extrusion blow molding process or coextrusion blow moldingprocess. In the case of multi-layer films or hollow articles,commercially available coupling agents may be used.

[0041] The starting polyamides for the polyamide molding compositionsaccording to the invention may be produced by known means in acontinuous or discontinuous process. A discontinuous process may be e.g.polymerization in an autoclave. A continuous process may be e.g.polymerization in a continuous tubular reactor. The productionpreferably takes place by a continuous process. To achieve highmolecular weights, as are often needed for use as a film material,polymerization in the melt can be followed by a post-condensation in thesolid phase. The addition of the poly-N-vinyllactam orpoly-N-vinylpyrrolidones takes place in the form of a homogeneoussolution after the last viscosity-building process step directly on tothe granules.

[0042] Alternatively, addition as a solid or liquid or solution duringcompounding, e.g. in a twin-screw extruder or kneader, is also possibleduring the production of compounds. As a further alternative, theaddition of the poly-N-vinyllactam or poly-N-vinylpyrrolidones ispossible in pure form or as a homogeneous solution, directly beforeprocessing suitable compounds on an injection-molding machine.

[0043] The molding compositions, films, hollow articles, profiles orinjection moldings according to the invention can be further processedor formed before their ultimate end use. Thus, for example, the filmsaccording to the invention may be thermo-formed. The films or hollowarticles according to the invention may be used e.g. for packagingpurposes. Films or hollow articles according to the invention may, forexample, be employed for packaging foodstuffs, such as meat and meatproducts, sausage, cheese, drinks etc. The films or hollow articlesaccording to the invention may also, for example, be employed forpackaging cosmetics, such as e.g. sun protection creams, or chemicals,such as e.g. plant protection agents. In addition, the hollow articlesaccording to the invention may be used as pipes or tanks. These can bee.g. pipes or tanks for fuels or oils for cars.

[0044] Laser transmission welded injection moldings may be used e.g. ashousings for electrical components and/or sensors.

[0045] The clear inhibition of crystallisation found here is achieved bythe addition of poly-N-vinyllactam or poly-N-vinylpyrrolidone orcopolymers consisting of vinyllactam, and/or vinylpyrrolidone as well asother vinyl monomers, such as e.g. vinyl acetate and/or vinylimidazoleand/or quaternised vinylimidazole and/or vinyl acrylate and/ormethacrylates, such as e.g. methyl methacrylate, sodium methacrylate orcyclohexyl methacrylate and/or acrylamide and/or acrylonitrile and/orN-vinylcarbazole and/or styrenes, such as e.g. p-aminostyrene or ahomogeneous solution of poly-N-vinyllactam or poly-N-vinylpyrrolidone,or copolymers consisting of vinyllactam and/or vinylpyrrolidone as wellas other vinyl monomers, such as e.g. vinyl acetate and/orvinylimidazole and/or quaternised vinylimidazole and/or vinyl acrylateand/or methacrylates, such as e.g. methyl methacrylate, sodiummethacrylate or cyclohexyl methacrylate and/or acrylamide and/oracrylonitrile and/or N-vinylcarbazole and/or styrenes, such as e.g.p-aminostyrene.

[0046] Surprisingly, the action of the solution of poly-N-vinyllactam orpoly-N-vinylpyrrolidones according to the invention occurs withadditions of as little as <500 ppm. Only the homogeneous distributionmakes extrusion into films possible, since only in this way mayincreased fish eye formation be avoided.

[0047] In the case of a special application, the polyamides according tothe invention may be adapted to form materials with specially adjustedcombinations of properties, alone or in combination with processingauxiliary substances, stabilisers, polymeric alloying materials (e.g.elastomers) or also reinforcing materials (such as e.g. mineral fillersor glass fibers). Blends with proportions of other polymers, e.g. ofpolyethylene, polypropylene or ABS, are also suitable. The properties ofthe polyamides may be improved by adding elastomers, e.g. in terms ofthe impact strength of e.g. reinforced polyamides. The many possiblecombinations enable a very large number of products to be obtained withwidely varying properties.

[0048] The polyamides produced according to the invention may also beused in a mixture with other polyamides and/or other polymers.

[0049] In addition, the polyamide molding compositions may also containflame retardants, such as e.g. phosphorus compounds, organic halogencompounds, nitrogen compounds and/or magnesium hydroxide, stabilizers,processing auxiliary substances, such as e.g. lubricants, nucleatingagents, stabilizers, impact modifiers, such as e.g. rubbers orpolyolefins and the like.

[0050] In addition to glass fibers, aramid fibers, mineral fibers andwhiskers are suitable as fibrous reinforcing fillers. Calcium carbonate,dolomite, calcium sulfate, mica, fluoromica, wollastonite, talcum andkaolin may be mentioned as suitable mineral fillers. To improve themechanical properties, the fibrous reinforcing fillers and the mineralfillers may be surface-treated.

[0051] The addition of the fillers may take place before, during orafter the polymerisation of the monomers to form the polyamide. If theaddition of the fillers according to the invention takes place after thepolymerization, it preferably takes place by addition to the polyamidemelt in an extruder. If the addition of the fillers according to theinvention takes place before or during the polymerisation, thepolymerization can comprise phases in which work is carried out in thepresence of 1 to 50 wt. % water.

[0052] When they are added, the fillers may already be present asparticles with the particle size ultimately occurring in the moldingcomposition. Alternatively, the fillers may be added in the form ofprecursors, from which the particles ultimately occurring in the moldingcomposition are formed only during the course of the addition orincorporation.

[0053] Suitable as fire or flame retardants are, for example, redphosphorus (DE-A-3 713 746 A 1 (=U.S. Pat. No. 4,877,823) and EP-A-299444 (=U.S. Pat. No. 5,081,222), brominated diphenyls or diphenyl ethersin combination with antimony trioxide and chlorinated cycloaliphatichydrocarbons (Dechlorane® plus from Occidental Chemical Co.), brominatedstyrene oligomers (e.g. in DE-A-2 703 419) and polystyrenes brominatedin the nucleus (e.g. Pyro-Check 68® from FERRO Chemicals).

[0054] As a synergist to the above-mentioned halogen compounds, forexample zinc compounds or iron oxides are used.

[0055] As another alternative, melamine salts in particular have proveda suitable flame retardant particularly for unreinforced polyamides.

[0056] In addition, magnesium hydroxide has long proved a suitable flameretardant for polyamide.

[0057] In addition to glass fibers, the polyamide molding compositionsmay additionally contain rubber-elastic polymers (often also referred toas an impact modifier, elastomer or rubber).

[0058] Sterically hindered phenols and/or phosphites, hydroquinones,aromatic secondary amines, such as diphenylamines, various substitutedrepresentatives of these groups and mixtures thereof in concentrationsof up to 1 wt. %, based on the weight of the thermoplastic moldingcompositions, are mentioned as examples of antioxidants and heatstabilisers.

[0059] Various substituted resorcinols, salicylates, benzotriazoles andbenzophenones may be mentioned as UV stabilizers, which are generallyused in quantities of up to 2 wt. %, based on the molding composition.

[0060] Sodium phenyl phosphinate, aluminium oxide, silicon dioxide andpreferably talcum, for example, may be used as nucleating agents.

[0061] Lubricants and mold release agents, which are conventionally usedin quantities of up to 1 wt. %, are preferably ester waxes,pentaerythritol stearate (PETS), long-chain fatty acids (e.g. stearicacid or behenic acid), the salts thereof (e.g. Ca or Zn stearate) andamide derivatives thereof (e.g. ethylenebisstearamide) or montan waxes,as well as low molecular weight polyethylene or polypropylene waxes.

[0062] Dioctyl phthalate, dibenzyl phthalate, butyl benzyl phthalate,hydrocarbon oils and N-(n-butyl)benzenesulfonamide may be mentioned asexamples of plasticizers.

[0063] Particularly preferred is the additional use of rubber-elasticpolymers (often also referred to as impact modifier, elastomer orrubber).

[0064] In general these are copolymers, which are preferably constructedfrom at least two of the following monomers: ethylene, propylene,butadiene, isobutene, isoprene, chloroprene, vinyl acetate, styrene,acrylonitrile and acrylates or methacrylates with 1 to 18 C atoms in thealcohol component.

[0065] These polymers are described e.g. in Houben-Weyl, Methoden derorganischen Chemie, vol. 14/1 (Georg-Thieme Verlag, Stuttgart, 1961),pages 392 to 406 and in the monograph by C. B. Bucknall, “ToughenedPlastics” (Applied Science Publishers, London, 1977).

[0066] Mixtures of rubber types may, of course, also be used.

[0067] Suitable as colorants are both organic and inorganic pigmentsand/or dyes. Carbon black is optionally a component of the pigment mixin very small quantities. The pigments/dyes and/or carbon blacks mayoptionally also be used as a batch.

[0068] Examples of inorganic pigments are antimony trioxide, antimonypentoxide, basic lead carbonate, basic lead sulfate or lead silicate,lithopones, titanium dioxide (anatase, rutile), zinc oxide, zincsulfide, metal oxides such as Berlin blue, lead chromate, leadsulfochromates, chromium antimony titanate, chromium oxides, ironoxides, cobalt blue, cobalt-chromium blue, cobalt-nickel grey, manganeseblue, manganese violet, molybdenum orange, molybdenum red,nickel-antimony titanate, ultramarine blue, as well as metal sulfidessuch as antimony trisulfide, cadmium sulfide, cadmium sulfoselenides,zirconium silicates, zirconium-vanadium blue and zirconium-praseodymiumyellow.

[0069] Examples of organic pigments are anthraquinone, azo, azomethine,benzanthrone, quinacridone, quinophthalone, dioxazine, flavanthrone,indanthrone, isoindoline, isoindolinone, methine, perinone, perylene,phthalocyanine, pyranthrone, pyrrolopyrrole and thioindigo pigments aswell as metal complexes of e.g. azo, azomethine or methine dyes or metalsalts of azo compounds.

[0070] Suitable as polymer-soluble dyes are, for example, dispersiondyes, such as those of the anthraquinone series, e.g. alkylamino, amino,arylamino, cyclohexylamino, hydroxy, hydroxyamino orphenylmercaptoanthraquinones, as well as metal complexes of azo dyes,particularly 1:2 chromium or cobalt complexes of monoazo dyes, as wellas fluorescent dyes, e.g. those of the benzothiazole, coumarin, oxarineor thiazine series.

[0071] The polymer-soluble dyes may also be used in combinations withfillers and/or pigments, particularly with inorganic pigments such astitanium dioxide.

[0072] Pigments and/or polymer-soluble dyes may be used. In the case ofdyeing molding compositions that have to be laser-translucent, the dyesor pigments used may, of course, have no or only very low absorption inthe NIR spectral range and should be compatible with the thermoplasticpolymers used according to the invention and not substantially impairtheir mechanical or other properties.

[0073] Suitable pigment additives are e.g. fatty acids with at least 12C atoms, such as behenic acid or stearic acid, their amides, salts oresters, such as aluminium stearate, magnesium stearate, zinc stearate ormagnesium behenate, as well as quaternary ammonium compounds, such astri(C₁-C₄)-alkylbenzylammonium salts, waxes, such as polyethylene wax,resin acids, such as abietic acid, colophony soap, hydrogenated ordimerised colophony, C₁₂-C₁₈ paraffin disulfonic acids or alkylphenols.

[0074] Preferred are dyes of the pyrazolone, perinone and anthraquinonetype, and of the methine, azo and coumarin type.

[0075] Also preferred are the metal-containing pigments, such as theinorganic pigments and the metal complexes of azo, azomethine or methinedyes, azomethine, quinacridone, dioxazine, isoindoline, isoindolinone,perylene, phthalocyanine, pyrrolopyrrole and thioindigo colorants andbismuth vanadate.

EXAMPLES

[0076] Test Methods

[0077] The isothermal crystallization time was measured usingdifferential calorimetry. The measurement of the film index takes placeby an optical evaluation system. Here, granules are extruded into a filmand defects in the film are characterized according to their size. Thefilm index is a value calculated from the number and size of thedefects, on which the defects have a weighted influence according totheir size.

[0078] Implementation and Results of the Laser Transmission Measurements

[0079] The sample sheets of the IR laser-absorbing and the IRlaser-transparent material were both tested using a transmissionmeasuring arrangement consisting of a spectrophotometer and a photometersphere, which detects both directly transmitted light and scatteredlight. For IR laser-transparent material with layer thicknesses ofbetween 1 and 3 mm, a transmission level of typically 20-70% isdisplayed.

[0080] Materials Used

[0081] Durethan® B40 FA, commercially available polyamide from Bayer AG.

[0082] Durethan® B40 F, commercially available polyamide 6 from Bayer AG

[0083] Durethan® B 38 FKA, commercially available polyamide 6 from BayerAG

[0084] Durethan® B 30 F, commercially available polyamide 6 from BayerAG

[0085] PEG 400 (Polyethyleneglycol 400) [25322-68-3-], commerciallyavailable product from Aldrich

[0086] Luviskol K25 (Polyvinylpyrrolidone K25) [9003-39-8], commerciallyavailable product from Aldrich

[0087] Luviskol K30 (Polyvinylpyrrolidone K30) [9003-39-8], commerciallyavailable product from Aldrich

[0088] Mistron Vapor RP6, commercially available talcum from Luzenac

[0089] Luviskol K90 (Polyvinylpyrrolidone K90), commercially availableproduct from BASF AG

[0090] Glass fibers CS 7928, commercially available chopped strands fromBayer AG

[0091] All % and ppm data are by weight, based on the overallcomposition.

Example 1

[0092] A solution of 468 ppm PEG and 33 ppm Luviskol K90 is added to 6kg of a commercially available polyamide (Durethan® B40F) in a spiralmixer at 80° C. and mixed for 2 h at 80° C.

[0093] In an extruder with a flat film die under a melt pressure of 36bar, at a melt temperature of 257° C. and a screw speed of 30 rpm, thematerial is extruded into a film with a width of approx. 300 mm and athickness of approx. 50 μm. The chill roll temperature is 90° C.

Example 2

[0094] A solution of 935 ppm PEG 400 and 123 ppm Luviskol K90 is addedto 6 kg of a commercially available polyamide (Durethan® B40F) in aspiral mixer at 80° C. and mixed for 2 h at 80° C.

[0095] The extrusion conditions selected are as in Example 1.

Example 3

[0096] A solution of 877 ppm PEG 400, 150 ppm talcum and 65 ppm LuviskolK90 is added to 6 kg of a commercially available polyamide (Durethan®B40F) in a spiral mixer at 80° C. and mixed for 2 h at 80° C.

[0097] The extrusion conditions selected are as in Example 1.

Example 4

[0098] A solution of 826 ppm PEG 400 and 173 ppm Luviskol K90 is addedto 6 kg of a commercially available polyamide (Durethan® B40F) in aspiral mixer at 80° C. and mixed for 2 h at 80° C.

[0099] The extrusion conditions selected are as in Example 1.

Example 5

[0100] A solution of 244 ppm PEG 400 and 122 ppm Luviskol K30 is addedto 6 kg of a commercially available polyamide (Durethan® B4° F.) in aspiral mixer at 80° C. and mixed for 2 h at 80° C.

[0101] The extrusion conditions selected are as in Example 1.

Example 6

[0102] A solution of 205 ppm PEG 400 and 123 ppm Luviskol K25 is addedto 6 kg of a commercially available polyamide (Durethan® B40F) in aspiral mixer at 80° C. and mixed for 2 h at 80° C.

[0103] The extrusion conditions selected are as in Example 1.

Example 7

[0104] A solution of 667 ppm PEG 400 and 333 ppm Luviskol K30 is addedto 6 kg of a commercially available polyamide (Durethan® B40F) in aspiral mixer at 80° C. and mixed for 2 h at 80° C.

[0105] The extrusion conditions selected are as in Example 1.

Example 8

[0106] A solution of 625 ppm PEG 400 and 375 ppm Luviskol K25 is addedto 6 kg of a commercially available polyamide (Durethan® B40F) in aspiral mixer at 80° C. and mixed for 2 h at 80° C.

[0107] The extrusion conditions selected are as in Example 1.

Example 9

[0108] Unreinforced PA 6 (Durethan B30F, a commercial product from BayerAG) was processed with the additives stated in Table 3 (with addition ofLuviskol K90) and glass fibers by compounding in a twin screw extruder(ZSK 32 from Werner und Pfleiderer) at a melt temperature of approx.270° C. to form a thermoplastic molding composition. The melt was thenspun off through a water bath and granulated. The granules obtained wereprocessed into rectangular test specimens (125 mm×12.5 mm×1.5 mm) on aninjection-molding machine of the Arburg 320-210-500 type underconditions conventional for molding compositions (melt temperatures of280° C., mold temperatures 80° C.) for laser transmission measurements.

Comparative Example 1

[0109] 6 kg of a commercially available polyamide (Durethan® B40 F) aresubjected to heat stress as in Example 1 and processed as in Example 1.

Comparative Example 2

[0110] 6 kg of a commercially available polyamide (Durethan® B40 FA) aresubjected to heat stress as in Example 1 and processed as in Example 1.

Comparative Example 3

[0111] 6 kg of a commercially available polyamide (Durethan® B40 FKA)are subjected to heat stress as in Example 1 and processed as in Example1.

Comparative Example 4

[0112] 173 ppm of Luviskol K90 are added to 6 kg of a commerciallyavailable polyamide (Durethan® B40F) in a spiral mixer at approx. 140°C. and mixed for 2 h at 140° C.

Comparative Example 5

[0113] 6 kg of a commercially available polyamide (Durethan® B40F) aresubjected to heat stress in a spiral mixer as in Comparative Example 4.

Comparative Example 6

[0114] Unreinforced PA 6 (Durethan B30F, a commercial product from BayerAG) was processed with the additives stated in Table 3 (without theaddition of Luviskol) and glass fibers by compounding in a twin screwextruder (ZSK 32 from Werner und Pfleiderer) at a melt temperature ofapprox. 270° C. to form a thermoplastic molding composition. The meltwas then spun off through a water bath and granulated. The granulesobtained were processed into test pieces (rectangular test specimens,125 mm×12.5 mm×1.5 mm) on an injection-molding machine of the Arburg320-210-500 type under conditions conventional for molding compositions(melt temperatures of 280° C., mold temperatures 80° C.) for lasertransmission measurements.

[0115] The products from Comparative Examples 1, 2 and 3 as well asExamples 1 to 8 were investigated with respect to their isothermalcrystallization times. The data are compiled in the following tables.TABLE 1 Isothermal crystallization times at 200° C. Polyvinyl-Isothermal PEG 400 Polyvinyl- pyrrolidone crystallization contentpyrrolidone content time at 200° C. Test [ppm] type [ppm] [min]Comparative 0 — 0 4.7 Example 1 Comparative 0 — 0 4.0 Example 2Comparative 0 — 0 3.0 Example 3* Comparative 400 — 0 4.2 Example 4Example 1 468 K90 33 5.2 Example 2 935 K90 65 5.9 Example 3* 877 K90 1233.7 Example 4 826 K90 173 6.7 Example 5 244 K30 122 5.8 Example 6 205K25 123 5.7 Example 7 665 K30 333 5.8 Example 8 625 K25 375 5.5

[0116] TABLE 2 Comparison of film indices Polyvinyl- PEG 400 Polyvinyl-pyrrolidone content pyrrolidone content Test [ppm] type [ppm] Film indexComparative 0 K90 174 9968 Example 4 Comparative 0 — 0 338 Example 5Example 4 826 K90 174 84

[0117] TABLE 3 Composition of the molding compositions for processing byinjection molding / laser transmission welding Cp. Ex. 9 Ex. 10 Ex. 11Ex. 12 Ex. 13 Ex. 6 PA6, [%] 69.948 69.3 68.8 68.7 67.8 70 additives¹⁾Glass [%] 30 30 30 30 30 30 fibers Bayer CS 7928 Luviskol [%] 0.052²⁾0.7 1.2 1.7 2.2 K90

[0118] The laser transmission values of the compositions according toComparative Example 6 and Examples 9-12 were determined in the freshlymolded state and after tempering (post-crystallization 4 h/120° C.). Thedata are compiled in the following tables. TABLE 4 Results of thetransmission measurements* on 1.5 mm thick test pieces Test specimenWavelength thickness [nm] [mm] Pretreatment of samples Ex. 9 Ex. 10 Ex.11 Ex. 12 Ex. 13 Cp. Ex. 6 810 1.5 None, freshly molded 59 60 61 61 6256 1065 1.5 None, freshly molded 64 66 66 67 68 62 810 1.5 Tempered 4 h120° C. 54 56 56 56 57 53 1065 1.5 Tempered 4 h 120° C. 60 62 62 63 6459

[0119] Since all the samples are made of very strongly scatteringmaterial, the total transmission was evaluated as the sum of direct anddiffuse transmission.

[0120] The samples corresponding to the comparative examples have muchlower transmission at 1000 nm and in the adjacent wavelength range,while the samples according to the invention of Examples 1-4 withLuviskol additive display significantly higher transmission.

[0121] Although the invention has been described in detail in theforegoing for the purpose of illustration, it is to be understood thatsuch detail is solely for that purpose and that variations can be madetherein by those skilled in the art without departing from the spiritand scope of the invention except as it may be limited by the claims.

What is claimed is:
 1. A molding composition comprising A) 90-99.995 wt.% polyamide B) 0.005-5 wt. % vinyl (co)polymer C) 0-5 wt. % solvent, thewt. % all occurrences being relative to the weight of the composition.2. The composition according to claim 1 wherein A) is present in anamount of 95-99.994 wt. %, B) is present in an amount of 0.005-1 wt. %and C) is present in an amount of 0.001-1 wt. %.
 3. The compositionaccording to claim 1 wherein A) is present in an amount of 99-99.965 wt.% and B) is present in an amount of 0.005-0.8 wt. % and C) is present inan amount of 0.03-0.4 wt. %.
 4. The composition according to claim 1further containing at least one member selected from the groupconsisting of fillers, reinforcing fillers, conventional additives andcolorants.
 5. The composition according to claim 1 wherein B) is atleast one member selected from the group consisting ofpoly-N-vinyllactam, poly-N-vinylpyrrolidone copolymers of vinyllactamand copolymers of vinylpyrrolidone.
 6. The composition according toclaim 1 wherein A) is polyamide
 6. 7. The composition according to claim1 wherein the solvent is a member selected from the group consisting ofwater, alcohol, ketone, glacial acetic acid, chlorinated hydrocarbon andphenol.
 8. A molded article comprising the composition of claim
 1. 9. Alaser-transmission welded molding comprising the composition of claim 1.10. A method of use of the molding composition of claim 1 in films,hollow articles, injection moldings and extruded profiles.